All of those except D and E?
I think there's so many who are trying to make music, the scene's gotten so big, it's hard to get noticed. Then there's the fact that a lot of it is generic elctric music, which isn't that good, or if it is good, they're still stuck in the shadow of the musicians who came before them.
Another thing, I feel like the early Brony musicians took more risks when they made their music.